Allogenic/xenogenic implants and methods for augmenting or repairing intervertebral discs

ABSTRACT

Allogenic or xenogenic materials are used to provide intervertebral disc nucleus implants and/or annular plugs. The allogenic or xenogenic materials comprise natural disc annulus material, which may have a portion of the anterior longitudinal ligament attached. The tissue may be used “as is” without an additional core or covering, or it may be used in combination with other materials. The material may be rolled, folded, layered and/or sutured, stapled, or glued to provide a solid plug of natural biological material. The implant may be provided as a dehydrated, substantially rod-shaped segment having a diameter less than the diameter of the hydrated material, and may have one or more ends of the dehydrated rod terminate with a further reduced diameter portion, preferably a point.

FIELD OF THE INVENTION

The present invention relates generally to implants and methods forreconstructing intervertebral discs, and more particularly to the use ofallogenic or xenogenic tissue to augment or repair an intervertebraldisc.

BACKGROUND OF THE INVENTION

It is known that intervertebral discs are prone to injury anddegeneration. For example, herniated discs are common, and typicallyoccur when normal wear, or exceptional strain, causes a disc to rupture.Degenerative disc disease typically results from the normal agingprocess, in which the tissue gradually looses its natural water andelasticity, causing the degenerated disc to shrink and possibly rupture.

Intervertebral disc injuries and degeneration are frequently treated byreplacing or augmenting the existing disc material. Currentintervertebral disc implants tend to utilize synthetic materials,particularly hydrogels, to augment or replace the original disc. Thesesynthetic materials are commonly covered with textured fabrics whoserough surfaces may accelerate wear of the encapsulated hydrogel or thebone endplates of the intervertebral body. Such wear may generate wearparticles, and can cause adverse biological responses such as osteolysisin the vertebral body endplate bone and subsequent subsidence of theimplant.

For example, reports on the use of prosthetic nucleus replacementdevices with polyethylene mesh jackets have indicated subsidence ofthese devices into the endplates of the vertebral bodies. Subsidence isalso due to the rigid compliance of the jacket and hard hydrogel core.This modulus mismatch with the vertebral bone, combined with the otherdesign features mentioned above, contributes to implant subsidence.

To avoid the problems associated with synthetic materials, naturalmaterials may be used to repair or augment intervertebral discs. Forexample, U.S. patent application Ser. No. 10/245,955, incorporatedherein by reference, discloses the use of natural collagen-basedmaterials to repair and/or augment intervertebral discs.

The use of natural collagen-based materials to repair and/or augmentintervertebral discs finds particular utility when used to provideannular plugs and/or nucleus implants that have the characteristics ofnatural tissue yet remain securely in place.

In view of the above it can be seen that a need exists for improvedannular plugs and/or nucleus implants made of natural collagen-basedmaterials, and particularly of allogenic or xenogenic materials. Thepresent invention addresses that need.

SUMMARY OF THE INVENTION

One aspect of the present invention uses allogenic or xenogenic discannulus material to provide intervertebral disc nucleus implants and/orannular plugs. The allogenic or xenogenic disc annulus material may be awhole annulus, or it may be a segment of an annulus such as the anteriorportion. The annulus material is preferably free, or at leastsubstantially free, of both disc nucleus material and disc endplatematerial. In some embodiments a portion of the anterior longitudinalligament may be included in the implant.

The tissue may be used “as is” without an additional core or covering,or it may be used in combination with other materials. The anteriorlongitudinal ligament may be wrapped around the disc annulus material toprovide protection and support for the implant, and to improve theimplant's strength and stability. The material may be rolled, folded,dehydrated, compressed, layered, sutured, stapled, glued, etc., toprovide an implant having a desired implant size and geometry.

In one preferred embodiment, a segment of allogenic or xenogenicanterior annulus is straightened, compressed, and dehydrated to providea rod-shaped implant having a diameter that is smaller than the diameterof the uncompressed material. At least one end of the implant ispreferably pointed to facilitate pushing the implant through a smallhole in the disc to be repaired. The implant is rehydrated afterimplantation to provide the desired support, and to prevent the implantfrom being expelled from the repaired disc.

One object of the present invention is to provide intervertebral discimplants made of materials that more closely match the tissue beingaugmented, repaired, or replaced. Additional features and benefits ofthe present invention shall become apparent from the followingdescription of the preferred embodiments.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a side elevational view of an intervertebral disc, with theanterior longitudinal ligament attached, between two adjacent vertebrae.

FIG. 2 is a side elevational view of a natural disc material accordingto one embodiment of the present invention, with a piece of anteriorlongitudinal ligament attached and extending both above and below thedisc.

FIG. 3 is a side elevational view of a natural disc material accordingto one embodiment of the present invention, with a piece of anteriorlongitudinal ligament attached and extending only in one direction fromthe disc.

FIG. 4 is a top plan view of a natural disc material according to oneembodiment of the present invention, with the anterior longitudinalligament attached.

FIG. 5 is a side elevational view of a natural disc implant according toone embodiment of the present invention, before the anteriorlongitudinal ligament has been folded and secured around the implant.

FIG. 6 is a top plan view of the natural disc implant of FIG. 5.

FIG. 7 is a top plan view of the natural disc implant of FIG. 5, afterthe anterior longitudinal ligament has been folded and secured aroundthe implant.

FIG. 8 is a side elevational view of the natural disc implant of FIG. 5,after the anterior longitudinal ligament has been folded and securedaround the implant.

FIG. 9 is a side elevational view of a natural disc implant according toone embodiment of the present invention, before the anteriorlongitudinal ligament has been folded and secured around the implant.

FIG. 10 is a top plan view of the natural disc implant of FIG. 9.

FIG. 11 is a top plan view of the natural disc implant of FIG. 9, afterthe anterior longitudinal ligament has been folded and secured aroundthe implant.

FIG. 12 is a side elevational view of the natural disc implant of FIG.9, after the anterior longitudinal ligament has been folded and securedaround the implant.

FIG. 13 is a side elevational view of a pair of natural disc implantsaccording to one embodiment of the present invention, before theanterior longitudinal ligament has been folded and secured around theimplants.

FIG. 14 is a side elevational view of the natural disc implant of FIG.13, after the anterior longitudinal ligament has been folded and securedaround the implant.

FIG. 15 is a top plan view of the natural disc implant of FIG. 13, afterthe anterior longitudinal ligament has been folded and secured aroundthe implant.

FIG. 16 is a side elevational view of a natural disc implant accordingto one embodiment of the present invention.

FIG. 17 is a top plan view of the natural disc implant of FIG. 16.

FIG. 18 is a side elevational view of the implant of FIG. 16 after theanterior longitudinal ligament is wrapped and secured around theimplant.

FIG. 19 is a top plan view of the implant of FIG. 16 after the anteriorlongitudinal ligament is wrapped and secured around the implant.

FIG. 20 is a side elevational view of a natural disc implant accordingto one embodiment of the present invention.

FIG. 21 is a top plan view of the natural disc implant of FIG. 20.

FIG. 22 is a top plan view of the natural disc implant of FIG. 20, afterthe anterior longitudinal ligament has been folded and secured aroundthe implant.

FIG. 23 is a side elevational view of the natural disc implant of FIG.20, after the anterior longitudinal ligament has been folded and securedaround the implant.

FIG. 24 is a top plan view of a natural disc implant according to oneembodiment of the present invention.

FIG. 25 is a top plan view of a natural disc implant according to oneembodiment of the present invention, after the implant has been preparedfor use.

FIG. 26 is a top plan view of a natural disc implant according to oneembodiment of the present invention, after the implant has been preparedfor use.

FIG. 27 is a top plan view of a natural disc implant according to oneembodiment of the present invention, after the implant has been preparedfor use.

FIG. 28 is a top plan view of a natural disc implant according to oneembodiment of the present invention, after the implant has been preparedfor use.

FIG. 29 is a top plan view of a natural disc implant according to oneembodiment of the present invention, after the implant has been preparedfor use.

FIG. 30 is a side elevational view of the implant of FIG. 29.

FIG. 31 is a side elevational view of an annular plug of the presentinvention, according to one preferred embodiment.

FIG. 32 is a top plan view of the annular plug of FIG. 31.

FIG. 33 is a top plan view of an annular plug of the present invention,according to one preferred embodiment.

FIG. 34 is a top plan view of the annular plug of FIG. 33, after theplug has been prepared for use.

FIG. 35 is a side elevational view of an annular plug of the presentinvention, according to one preferred embodiment.

FIG. 36 is a top plan view of the annular plug of FIG. 35.

FIG. 37 is a top plan view of the annular plug of FIG. 35, after theplug has been prepared for use according to one embodiment of thepresent invention.

FIG. 38 is a side elevational view of the annular plug of FIG. 35, afterthe plug has been prepared for use according to one embodiment of thepresent invention.

FIG. 39 is a top plan view of the annular plug of FIG. 35, after theplug has been prepared for use according to another embodiment of thepresent invention.

FIG. 40 is a side elevational view of the annular plug of FIG. 35, afterthe plug has been prepared for use according to another embodiment ofthe present invention.

FIG. 41 is a top plan view of an annular plug of the present invention,according to one preferred embodiment.

FIG. 42 is a top plan view of the annular plug of FIG. 41.

FIG. 43 is a top plan view of the annular plug of FIG. 41, after theplug has been prepared for use according to one preferred embodiment ofthe present invention.

FIG. 44 is a side elevational view of the annular plug of FIG. 41, afterthe plug has been prepared for use according to one preferred embodimentof the present invention.

FIG. 45 is a side elevational view of the annular plug of FIG. 41.

FIG. 46 is a top plan view of the annular plug of FIG. 45, after theplug has been prepared for use according to another embodiment of thepresent invention.

FIG. 47 is a side elevational view of the annular plug of FIG. 41, afterthe plug has been prepared for use according to another embodiment ofthe present invention.

FIGS. 48A-B shows a spinal implant according to the present invention,with FIG. 48A showing a complete disc annulus before compression anddehydration, and FIG. 48B showing a segment of disc annulus beforecompression and dehydration.

FIG. 49 shows a mold for compressing a spinal implant according to oneembodiment of the present invention.

FIG. 50 shows a mold being used to compress a spinal implant accordingto one embodiment of the present invention.

FIG. 51 shows a compressed, dehydrated spinal implant according to oneembodiment of the present invention.

FIG. 52 shows the compressed, dehydrated spinal implant of FIG. 51,after one end of the implant has been tapered to a point.

FIG. 53 shows an alternative mold for use in compressing a spinalimplant according to one embodiment of the present invention.

FIGS. 54-57 show a method of using the inventive spinal implants.

FIG. 54 shows a spinal implant according to one embodiment of thepresent invention just before it is implanted into a patient.

FIG. 55 shows the spinal implant of FIG. 54 as it enters the disc to berepaired.

FIG. 56 shows the spinal implant of FIG. 54 after implantation in a discnucleus space.

FIG. 57 shows the spinal implant of FIG. 54 after it has been rehydratedin the disc nucleus space.

FIG. 58 shows a pig disc prior to harvesting xenogenic disc annulusmaterial therefrom.

FIG. 59 shown the pig disc of FIG. 58, after the disc has been cut inhalf.

FIG. 60 shows the xenogenic annulus material that has been removed fromthe disc of FIG. 58.

FIGS. 61A-61C show the xenogenic annulus material of FIG. 60 before,during, and after rolling.

FIG. 62 shows xenogenic disc annulus material ready for implantation toaugment a disc nucleus.

FIG. 63 shows the xenogenic disc annulus material of FIG. 62 beinginserted into a disc space.

FIG. 64 shows a dissected disc containing the xenogenic annulus materialof FIG. 62.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

For the purpose of promoting an understanding of the principles of theinvention, reference will now be made to preferred embodiments andspecific language will be used to describe the same. It willnevertheless be understood that no limitation of the scope of theinvention is thereby intended, such alterations and furthermodifications of the disclosed methods and/or devices, and such furtherapplications of the principles of the invention as described herein,being contemplated as would normally occur to one skilled in the art towhich the invention relates.

As briefly described above, one aspect of the present invention providesmaterials and methods for augmenting or replacing an intervertebral discnucleus. Another aspect of the invention provides materials and methodsfor repairing or plugging an intervertebral disc annulus. For thepurposes of this disclosure, both the disc nucleus implant and the discannulus implant are referred to as intervertebral disc implants.

The intervertebral disc implants of the present invention compriseallogenic or xenogenic disc annulus material. The allogenic or xenogenicdisc annulus material is substantially free of both disc nucleusmaterial and disc endplate material. As will be discussed further below,the disc annulus material may be a whole disc annulus, or it may be onlya portion, or segment, of disc annulus. When only a segment of annulusis used, it may be a section from the anterior portion of the annulus,or it may be a portion from the lateral or posterior portion of theannulus.

In some embodiments the inventive implant comprises allogenic orxenogenic disc annulus material in combination with other materials. Forexample, implants comprising allogenic or xenogenic disc annulusmaterial may include other therapeutic agents and/or materials toimprove performance or facilitate implantation. In other embodiments theimplant consists of, or consist essentially of, allogenic or xenogenicdisc annulus material.

In some embodiments allogenic or xenogenic ligament material, andparticularly anterior longitudinal ligament material, is also used inthe implant. The ligament material is preferably material that isnaturally connected to the annulus being used for the implant.

In embodiments in which allogenic or xenogenic anterior longitudinalligament material is included, the anterior longitudinal ligament mayinclude portions that extend above and/or below the annulus when viewedfrom the side, providing a length of ligament material that may be usedto assist in forming the implant. In other embodiments the anteriorlongitudinal ligament is limited to the portion that lies adjacent tothe annulus, and thus does not extend above or below the annulus. When alonger portion of ligament is used, the length of the material ispreferably between about 0.5 cm and 2.5 cm, although shorter or longerlengths of anterior longitudinal ligament may be used. For example, insome embodiments the anterior longitudinal ligament may be long enoughto wrap completely around the allogenic/xenogenic disc (or piecethereof) to protect and stabilize the implant. In other embodiments, theanterior longitudinal ligament may be long enough to wrap completelyaround two or more allogenic/xenogenic discs (or piece thereof) toprotect and stabilize the formed implant.

For the purposes of this disclosure, the terms allogenic and xenogenicare used with respect to the host into which the tissue is to beimplanted. Accordingly, allogenic tissue is tissue that is geneticallydifferent, although its origin is from the same species as the patientinto which it's implanted. Similarly, xenogenic tissue is tissue whoseorigin is from a different species than the patient into which it'simplanted. In some embodiments the invention provides and uses allogenicor xenogenic disc material with allogenic or xenogenic anteriorlongitudinal ligament. In those embodiments, the disc material and theanterior longitudinal ligament may be allogenic/xenogenic with respectto the host, while still being autogenic with respect to each other ifthey're derived from the same genetic source.

To retrieve the allogenic or xenogenic tissue a complete disc may beremoved with the anterior longitudinal ligament attached. Preferably,the disc nucleus and any disc endplate material are removed so that onlythe annulus and attached anterior longitudinal ligament are retained. Inother embodiments only disc annulus material is retrieved.

The material may be kept hydrated, or it may be dehydrated orsemi-hydrated prior to implantation. Dehydrated tissue is particularlypreferred when it is desired to form the implant into a desired shapeprior to or during implantation into a patient. In those cases thedehydrated tissue is typically rehydrated after implantation, either bynaturally absorbing liquid from the environment into which it is placed,or by injecting a rehydration liquid into the implant during or aftersurgery. After rehydration the implant may retain its dehydrated shape,or it may change shape to fill or otherwise adapt to the space intowhich it has been implanted.

As previously indicated, the retrieved allogenic or xenogenic tissue maybe used whole, or it may be cut into pieces to provide a piece of tissuehaving an appropriate size for forming a desired implant. For example,allogenic or xenogenic disc annulus material may be used as an intact“ring” of material (with or without manipulation as to shape), or it maybe cut and straightened to provide a long “tube” of allogenic orxenogenic disc annulus material. Alternatively, allogenic or xenogenicdisc annulus material may be cut into segments that are smaller than acomplete annulus, and used with or without manipulation that way.Anterior annulus material is preferably included when only a segment ofannulus is used.

Regardless of whether the tissue is used whole or in pieces, the tissuemay be compressed, folded, rolled, or otherwise manipulated to provide adesired geometry. Moreover, the tissue may be sutured, stapled, glued,etc., to provide maintain the desired implant geometry. (For thepurposes of this document, the term “suture” refers to any means forsecuring a rolled or folded implant, or pieces thereof, in a specificgeometry, and includes using stitches, sutures, staples, glues, cements,and other means known to the art to be effective for holding or securingtissue.) Some examples of specific preferred geometries are identifiedin the Figures below.

Referring now to the drawings, FIG. 1 is a side elevational view of anintervertebral disc 10, with the anterior longitudinal ligament 11attached, between two adjacent vertebrae 12 and 13 respectively. Disc 10includes an annulus portion 14 and a disc nucleus 15. In the preferredembodiments of the present invention disc 10 is retrieved with anteriorlongitudinal ligament 11 attached, and is used to make a nucleus implantand/or a annular plug.

FIG. 2 is a side elevational view of a natural disc material 20,according to one embodiment of the present invention, with a piece ofanterior longitudinal ligament 21 attached and extending both above andbelow the disc. Disc material 20 includes a disc nucleus 22 and a discannulus 23. While in this illustration the piece of anteriorlongitudinal ligament 21 is not long enough to wrap completely arounddisc 20 to protect and stabilize the implant, the drawing is forillustrative purposes only, and is not intended to indicate the lengthof anterior longitudinal ligament 21 appropriate for that purpose.

FIG. 3 is a side elevational view of a natural disc material 30,according to one embodiment of the present invention, with a piece ofanterior longitudinal ligament 31 attached and extending only in onedirection from the disc. Disc material 30 includes a disc nucleus 32 anda disc annulus 33. Here to, the drawing is for illustrative purposesonly, and is not intended to indicate the length of anteriorlongitudinal ligament 21 appropriate to wrap completely around disc 20to protect and stabilize the implant.

FIG. 4 is a top plan view of a natural disc material 40, according toone embodiment of the present invention, with the anterior longitudinalligament 41 attached. Disc material 40 includes a disc nucleus 42 and adisc annulus 43.

FIG. 5 is a side elevational view of an allogenic/xenogenic disc implant50, according to one embodiment of the present invention. FIG. 6 is atop plan view of that same disc implant 50. In the illustratedembodiment, implant 50 consists essentially of a piece ofallogenic/xenogenic disc annulus material 52, with upwardly anddownwardly extending pieces of anterior longitudinal ligament 51attached. In FIGS. 5 and 6, anterior longitudinal ligament 51 and discannulus material 52 are shown before ligament 51 has been wrapped andsecured around the implant to form the desired implant geometry. In thisembodiment piece 52 does not include a whole disc annulus, but insteadincludes only a piece (or “segment”) of the annulus.

FIG. 7 is a top plan view of the allogenic/xenogenic disc implant 50 ofFIG. 5, after the anterior longitudinal ligament 51 has been wrapped andsecured around the implant as required to form the desired implantgeometry. FIG. 8 is a side elevational view of the wrapped and secureddisc implant of FIG. 7. As can be seen from the drawings, theallogenic/xenogenic disc implant of FIGS. 5-8 takes advantage of theanterior longitudinal ligament 51 by wrapping that ligament around theannulus material 52 to form a stronger, more stable implant. Optionally,ligament 51 is secured around annulus material 52 by stitching theligament material closed with sutures 54. In the most preferredembodiments implant 50 assumes a cube shape 55 with ligament 51partially or substantially covering annulus material 52 on four of thesix sides of the cube.

FIG. 9 is a side elevational view of an allogenic/xenogenic disc implant90, according to one embodiment of the present invention. FIG. 10 is atop plan view of that same disc implant 90. In the illustratedembodiment, implant 90 consists essentially of a wholeallogenic/xenogenic disc annulus 92, with upwardly and downwardlyextending pieces of anterior longitudinal ligament 91 attached. Discnucleus space 93 is located in the center of disc annulus 92, and isempty in the illustrated embodiment since the disc nucleus has beenremoved. In FIGS. 9 and 10, anterior longitudinal ligament 91 and discannulus material 92 are shown before ligament 91 has been wrapped andsecured around the implant to form the desired implant geometry.

FIG. 11 is a top plan view of allogenic/xenogenic disc implant 110,which is made by wrapping anterior longitudinal ligament 91 aroundannulus 92 and securing the free ends together to form the desiredimplant geometry. FIG. 12 is a side elevational view of the wrapped andsecured disc implant of FIG. 11. As can be seen from the drawings, theallogenic/xenogenic disc implant of FIGS. 9-12 takes advantage ofanterior longitudinal ligament 91 by wrapping that ligament around theannulus material 92 to form a stronger, more compact implant. As can beseen from the drawings, disc nucleus space 93 is squeezed closed in theillustrated embodiment, further strengthening the implant and making itmore compact and stable.

As with the implant of FIGS. 5-8, ligament 91 may be secured aroundannulus material 92 by stitching the ligament material closed withsutures 94. In this embodiment though, a complete allogenic/xenogenicdisc annulus is used, with the ligament material holding the annulussqueezed shut to eliminate the opening that would otherwise exist in thecenter. In the most preferred embodiments implant 90 assumes a kidneyshape as shown in FIG. 11, with ligament 91 partially or substantiallycovering annulus material 92 around the midsection of the kidney.

FIG. 13 is a side elevational view of a pair of allogenic/xenogenicimplant pieces 131 and 132, according to one embodiment of the presentinvention. Each implant piece includes an allogenic/xenogenic discannulus 133 and 134, respectively, and a piece of anterior longitudinalligament 135 and 136. The ligament material preferably extends in onlyone direction from the annulus, as shown in the Figures.

FIGS. 14 and 15 shows allogenic/xenogenic implant 140 after it is formedby suturing implant pieces 131 and 132 together. One suture 141 is usedto join pieces 131 and 132 at the bottom of the ligament pieces 135 and136. Another suture 142 is used to secure the other ends of ligamentpieces 135 and 136, which are pulled over annulus pieces 133 and 134.The resulting implant 140 has a thickness double the thickness of asingle layer implant such as those shown in FIGS. 7 and 11. In anembodiment corresponding to the embodiment shown in FIG. 11, a pair ofwhole allogenic/xenogenic annuli are used, with the anteriorlongitudinal ligaments being stitched together to hold the two piecestogether.

FIGS. 16-18 show another embodiment of the present invention, with FIG.16 showing a side elevational view of allogenic/xenogenic disc implant160, according to one embodiment of the present invention. FIG. 17 is atop plan view of that same disc implant 160. In the illustratedembodiment, implant 160 consists essentially of a segment ofallogenic/xenogenic disc annulus material 162, with the piece ofanterior longitudinal ligament 161 attached and extending in only onedirection from the annulus. In FIGS. 16 and 17, anterior longitudinalligament 161 and disc annulus material 162 are shown before ligament 161has been wrapped and secured around the implant to form the desiredimplant geometry.

FIG. 17 is a top plan view of the allogenic/xenogenic disc implant 160of FIG. 16, after the anterior longitudinal ligament 161 has beenwrapped and secured around the implant as required to form the desiredimplant geometry. FIG. 18 is a side elevational view of the wrapped andsecured disc implant of FIG. 17. As can be seen from the drawings, theallogenic/xenogenic disc implant of FIGS. 16-17 takes advantage of theanterior longitudinal ligament 161 by wrapping that ligament around theannulus material 162 to form a stronger, more stable implant.Optionally, ligament 161 is secured around annulus material 162 bystitching the ligament material closed with sutures 164. In the mostpreferred embodiments implant 160 assumes a cube or box shape withligament 161 partially or substantially covering annulus material 162 onfour of the six sides of the implant.

FIGS. 20-23 show an embodiment that is similar in many respects to theembodiment of FIGS. 9-12, but with the anterior longitudinal ligamentnot including pieces that extend away from the allogenic/xenogenicannulus. Accordingly, FIGS. 20 and 21 show an allogenic/xenogenic tissue200, including whole annulus 202 and anterior longitudinal ligament 201.

In FIG. 22 it can be seen that disc nucleus space 203 is squeezed closedin the illustrated embodiment, strengthening the implant and making itmore compact in a manner similar to that shown in FIG. 9. In FIG. 22however, anterior longitudinal ligament 201 is not wrapped around discannulus 202, so sutures 221 are used to secure the two halves of annulus202 together. This closes disc nucleus space 203, and provides thedesired compact geometry.

FIG. 24 shows spinal implant 240, which comprises allogenic/xenogenicannulus 242, anterior longitudinal ligament 241, and empty nucleus space243. In this embodiment annulus 242 is cut by cut 245 so that theannulus can be rolled up into a stronger, more compact implant having adesired geometry.

FIG. 25 shows the implant of FIG. 24 after it is rolled up as describedabove. The implant may be secured by sutures 244, which hold the implantin its rolled-up form. If the anterior longitudinal ligament is providedas a flap extending from the annulus, the rolled-up implant may becovered with the flap as shown in FIG. 26.

FIGS. 27 and 28 show alternative embodiments of the implants of thepresent invention. In these embodiments the implant is preferablydehydrated after the desired geometry is obtained, so that thedehydrated implant will maintain the desired geometry at least until itis rehydrated after implantation.

FIG. 29 shows an embodiment of the present invention where theallogenic/xenogenic material 292 is covered with a jacket or wrap 297that is not formed from attached anterior longitudinal ligament. Thejacket or wrap may be natural material, and may be allogenic orxenogenic material, or it may be a synthetic material having theproperties desired for successful implantation. As with the embodimentspreviously described, the jacket or wrap strengthens and protects theimplant, and helps it maintain a desired geometry. FIG. 30 shows thewrapped implant of FIG. 29 from a side elevational view.

In addition to the nucleus implants described above, annular plugs areprovided by other aspects of the present invention. Such plugs aregenerally used to plug a hole in the annulus, particularly to retain anatural or synthetic nucleus within the annular ring. As with thenucleus implants, the annular plugs are made of allogenic or xenogenictissue, and particularly of a whole or section of allogenic or xenogenicannulus, and one or more pieces of allogenic or xenogenic anteriorlongitudinal ligament.

FIGS. 31-32 show an annular plug according to one preferred embodimentof the present invention. Plug 310 includes allogenic/xenogenic anteriorlongitudinal ligament 311 attached to allogenic/xenogenic annulusmaterial 312. In this embodiment the flap of anterior longitudinalligament serves as a cap to keep the implant from being pushed or pulledthrough the annulus into the nucleus space. In the most preferredembodiments anterior longitudinal ligament 311 is secured to the annulusinto which it's implanted by suturing the ligament to the outside of theannulus.

FIGS. 33-34 show an annular plug according to another preferredembodiment of the present invention. Plug 330 includesallogenic/xenogenic anterior longitudinal ligament 331 attached toallogenic/xenogenic annulus material 332. In this embodiment annulusmaterial 332 is a longer section of annulus than was used for theembodiment above, allowing the two ‘arms” 335 and 336 of the annulusmaterial to be folded together to form a thicker plug. Preferably, arms335 and 336 are sutured together with sutures 334 to hold the annularplug in a desired geometry.

FIGS. 35-40 show additional embodiments of the inventive annular plug.All of these embodiments begin with a complete allogenic/xenogenicannulus, as shown in FIGS. 35 and 36. The plug can adopt theconfiguration shown in FIGS. 37 and 38 by dehydrating the implant inthat desired configuration, or it can adopt the configuration shown inFIGS. 39 and 40 by suturing the empty nucleus space closed.

FIGS. 41-47 show additional embodiments of the annular plug of thepresent invention. In these embodiments a whole allogenic/xenogenicannulus 412 is used, but the annulus is cut with a cut 415 so that theannulus can be more easily folded together. FIGS. 41 and 42 show oneembodiment of allogenic/xenogenic annulus 412 after cut 415 is made, butbefore the sections of annulus are moved to the desired configurations.In FIG. 42 the anterior longitudinal ligament has pieces that extendaway from the annulus, as previously described. Accordingly, plug 420includes anterior longitudinal ligament 421 having free ends 426 and 427extending outward from the annulus material 422. When the two pieces ofannulus 412 are folded together and sutured as shown in FIGS. 43 and 44,the plug may be used to plug a hole in an annulus with free ends 426 and427 being used to secure the plug to the annulus into which it isimplanted.

FIGS. 45-47 show an embodiment similar to that above, but with anteriorlongitudinal ligament 451 not having pieces that extend away from theannulus. Accordingly, the two arms of the cut annulus may be foldedtogether over the anterior longitudinal ligament, and are preferablysutured together with sutures 461. The two arms 466 and 467 of the cutannulus 451 may be used to retain the plug from being pushed through theannulus into which it is implanted.

FIGS. 48-52 show one preferred embodiment of making an implant accordingto the present invention. In that embodiment, as shown in FIG. 48, alength of disc annulus material is formed from either a compressed wholedisc annulus 481 (FIG. 48A) or a straightened segment of disc annulus482 (FIG. 48B). Mold 490 of a porous material, such as a surgical steelmesh, having openings 491 large enough for water to pass through, isplaced around the disc annulus material, and is used to compress thematerial radially inward. By pushing mold 490 inward around disc annulusmaterial 481, the material can be compressed to a more compact size, asshown by implant 501. The illustrated compressed implant 501 comprisesan implant having a middle portion 502, and two end portions 503 and504.

In the preferred embodiment, compressed implant 501 is dehydrated sothat it retains its compact shape. After dehydration, implant 501 may befurther shaped, such as by providing end 503 with a reduced diameter,such as a rounded end 506 or a point 507.

In some embodiments the mold is a two-piece mold as shown in FIG. 48. Inother embodiments the “mold” may be simply a one-piece constructionssuch as a porous sheet 530. When a porous sheet is used, the “mold” maybe compressed around the implant by rolling sheet 530 ever tighter, sothat the diameter of the inside of the mold is reduced.

To make and use the inventive implants, the implant material is firstretrieved from a suitable subject, which is preferably a cadaver. Thematerial is cut to size, if necessary, and is fashioned into a desiredimplant geometry. The desired geometry may be maintained by suturing theimplant into a desired shape, and/or by dehydrating and/or freeze dryingthe implant while the desired shape is maintained.

The implant is then surgically implanted into a patient, using surgicaltechniques known to persons skilled in the art. When the implant is anucleus implant, the defective nucleus may first be removed before thereplacement nucleus is implanted, or the nucleus implant may be used toaugment the original nucleus. When the implant is an annular plug, theimplant is typically used to plug a hole in a disc annulus after surgeryon the nucleus contained therein. The annular plug holds a repaired orreplaced nucleus within the annulus ring, preventing migration of therepaired or replaced nucleus from within disc annulus.

In one preferred embodiment, a dehydrated, rod-shaped implant 540 with apoint 541 at one end is used by first piercing annulus 542 of the discto be augmented or repaired, as shown in FIG. 54. A needle (not shown)is preferably used for that purpose. Implant 540 is positioned in aguide tube 543 to facilitate implantation.

The point 541 of implant 540 is pushed through the puncture so that theend of implant 540 enters the disc nucleus space 545, as shown in FIG.55.

Dehydrated implant 540 is deposited in the disc nucleus space 545 asshown in FIG. 56, for example by using a plunger 561 to push the implantfrom the needle. After the implant is in position, it rehydrates toacquire its normal size, as shown in FIG. 57. The rehydrated implantdoes not fit back through the small puncture opening, and it thereforeretained in the disc nucleus space.

EXAMPLE

A feasibility experiment was performed to demonstrate the efficacy ofdisc augmentation using a dehydrated disc annulus. In the study, pigdisc annulus was harvested, dehydrated into an elongated shape, cut intoshorter sections, inserted into another pig disc, and allowed toreconstitute within the disc space. The augmented pig disc was thendissected for observation.

As to the details of the experiment, pig discs were sectioned from a pigspine for the study, as shown in FIG. 58. The disc was cut into twohalves right at one endplate surface to preserve as much annulus aspossible, as shown in FIG. 59. The anterior annulus was removed bysectioning right at the opposite endplate, as shown in FIG. 60. Theannulus was rolled up in a lint-free paper for drying and shaping, asshown in FIGS. 61A-61C. The annulus specimen was placed in thedesiccator for 3 days. The dehydrated annulus was removed from thepaper, to provide the dehydrated disc annulus shown in FIG. 62. A probewas used to dilate a channel through the annulus of the treated disc,and the dried annulus was cut into appropriate lengths and was insertedinto the disc space through the dilated annulus channel, as shown inFIG. 63. The treated pig disc was placed in saline and stored inrefrigerator for 20 hours and then in a 37° C. bath for 4 hours. Thetreated pig disc was dissected for examination.

It was found that the rigid elongated segments of pig annulus absorbedwater within the disc space, swelled up, and turned into larger and morecompliant annulus tissues, as shown in FIG. 64. Effective discaugmentation was obtained. Moreover, the reconstituted and enlargedannulus tissues remained within the augmented disc space, and were notexpelled through the channel in the annulus.

While the invention has been illustrated and described in detail in thedrawings and foregoing description, the same is to be considered asillustrative and not restrictive in character, it being understood thatonly the preferred embodiment has been shown and described and that allchanges and modifications that come within the spirit of the inventionare desired to be protected.

1. A method of augmenting or replacing an intervertebral disc nucleus,said method comprising the steps of: (a) providing an intervertebraldisc implant comprising allogenic or xenogenic disc annulus materialthat is substantially free of both disc nucleus material and discendplate material; and (b) implanting said intervertebral disc implantin an intervertebral disc nucleus space; wherein said intervertebraldisc implant comprises allogenic or xenogenic disc annulus material thatcomprises a whole disc annulus; and wherein said intervertebral discimplant further includes allogenic or xenogenic anterior longitudinalligament.
 2. A method according to claim 1 wherein said allogenic orxenogenic anterior longitudinal ligament is attached to said allogenicor xenogenic disc material.
 3. A method according to claim 1 whereinsaid allogenic or xenogenic anterior longitudinal ligament has free endsextending outward from said allogenic or xenogenic disc material.
 4. Amethod according to claim 3 wherein said free ends of said allogenic orxenogenic anterior longitudinal ligament are wrapped around saidallogenic or xenogenic disc annulus material.
 5. A method according toclaim 3 wherein the free ends of the allogenic or xenogenic anteriorlongitudinal ligament are secured together.
 6. A method according toclaim 5 wherein the free ends of the allogenic or xenogenic anteriorlongitudinal ligament are secured together with sutures, staples, or anadhesive.
 7. A method of augmenting or replacing an intervertebral discnucleus, said method comprising the steps of: (a) providing anintervertebral disc implant comprising allogenic or xenogenic discannulus material that is substantially free of both disc nucleusmaterial and disc endplate material; and (b) implanting saidintervertebral disc implant in an intervertebral disc nucleus space;wherein said intervertebral disc implant comprises allogenic orxenogenic disc annulus material that comprises a whole disc annulus;wherein said whole disc annulus is folded or rolled into a more compactstructure; wherein said whole disc annulus is dehydrated after foldingor rolling into a more compact structure.
 8. A method of augmenting orreplacing an intervertebral disc nucleus, said method comprising thesteps of: (a) providing an intervertebral disc implant comprisingallogenic or xenogenic disc annulus material that is substantially freeof both disc nucleus material and disc endplate material; and (b)implanting said intervertebral disc implant in an intervertebral discnucleus space; wherein said intervertebral disc implant comprisesallogenic or xenogenic disc annulus material that comprises a whole discannulus; wherein said whole disc annulus is folded or rolled into a morecompact structure; wherein said whole disc annulus is sutured or gluedafter folding or rolling into a more compact structure.
 9. A method ofaugmenting or replacing an intervertebral disc nucleus, said methodcomprising the steps of; (a) providing an intervertebral disc implantcomprising allogenic or xenogenic disc annulus material that issubstantially free of both disc nucleus material and disc endplatematerial; and (b) implanting said intervertebral disc implant in anintervertebral disc nucleus space; wherein said intervertebral discimplant comprises allogenic or xenogenic disc annulus material thatcomprises a whole disc annulus; wherein said whole disc annulus iswrapped in a jacket or wrap.
 10. A method according to claim 9 whereinsaid jacket or wrap is made of allogenic or xenogenic tissue.